Software-Hardware Trade-Offs: Application to A5/1 Cryptanalysis

This paper shows how a well-balanced trade-off between a generic workstation and dumb but fast reconfigurable hardware can lead to a more efficient implementation of a cryptanalysis than a full hardware or a full software implementation. A realistic cryptanalysis of the A5/1 GSM stream cipher is presented as an illustration of such trade-off. We mention that our cryptanalysis requires only a minimal amount of cipher output and cannot be compared to the attack recently announced by Alex Biryukov, Adi Shamir and David Wagner[2].